The present invention relates generally to powered positioning devices and, more particularly, to a powered pivot unit for moving or positioning industrial tooling.
Pivot units are commonly used in industrial applications for positioning tooling or work pieces during forming and machining operations. The previously known devices include a pneumatically or hydraulically actuated linear piston cylinder which causes one or more arms to move through a desired range of rotational motion to position the tool or work piece. These devices are often large clamps equipped with a toggle mechanism to achieve the rotational motion of the tool mount. Unfortunately, the toggle mechanism exhibits a torque per rotation angle curve which is not linear. Because the tooling or components to be rotated may weight 100 pounds or more and are often mounted 48 inches from the pivot point, existing pivot units may be unable to lift the tool.
Many conventional pivot units use a linear fluid cylinder coupled to the linkage to provide the lifting force. The conventional pivot units have cylinders separately attached to a body. The stroke of the fluid cylinder is directly proportional to the amount of rotation available at the tool mounting end. In an attempt to conserve the amount of actuating fluid required, existing manufacturers provide families of power pivot units equipped with a variety of differently sized cylinders. Long cylinders are used if large rotation angles are desired. Large diameter cylinders are used to lift heavy loads. Therefore, an undesirably large number of assemblies must be maintained in inventory to provide manufacturing flexibility. The use of elongated fluid cylinders also creates a relatively large and unwieldly pivot unit assembly which requires extra space in the end use manufacturing plant. Also, service of the linkage or toggle mechanism requires that the tool holding portion be disassembled.
In accordance with the teachings of the present invention, a preferred embodiment of a powered pivot unit includes a rotary actuator which provides a generally constant torque output over the entire operating range of pivot angles. In another aspect of the present invention, the rotary actuator includes a rotary vane which is positioned on an opposite side of the pivot point relative to the rotating arm assembly. This effectively counter-balances the tooling to reduce the torque required to lift or position the tool. A further aspect of the present invention provides 105 degrees of available rotation from a single rotary actuator. Because the powered pivot unit of the present invention utilizes a rotary vane within an arcuate chamber, less pressurized fluid is required to obtain the full 105 degrees of rotation when compared to linear fluid cylinders.
Yet another aspect of the present invention includes integral stops, shocks and switch assemblies which are adjustable in generally 15 degree increments throughout the full 105 degree range of rotation. In still another aspect of the present invention, a lock is provided at each 15 degree position to maintain the position of the tool when service is required.
Yet another aspect of the present invention is directed to ease of serviceability. Specifically, the actuator assembly may be replaced as a cartridge without disturbing the tool-to-arm assembly interface nor the pivot unit-to-bench interface. Therefore, the time to service the powered pivot unit of the present invention is minimized.
Furthermore, another aspect of the present invention employs a rotary actuator coupled to the rotating arm assembly through a pair of hub assemblies having drive keys which are mounted on a pair of jack screws. To disengage the drive keys from the rotary actuator, the jack screws are simply rotated in place. Advantageously, the jack screws and drive keys do not become separated from the hub assembly during the disengagement process. This simplified service method assures that these components do not become lost or contaminated by the surrounding environment.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the present invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.